synergist

[sin-er-jist, si-nur-] /ˈsɪn ər dʒɪst, sɪˈnɜr-/
noun
1.
Physiology, Medicine/Medical. a body organ, medicine, etc., that cooperates with another or others to produce or enhance an effect.
2.
Chemistry, Pharmacology. any admixture to a substance for increasing the effectiveness of one or more of its properties.
3.
Theology. a person who holds the doctrine of synergism.
Origin
1650-60; < Neo-Latin synergista < Greek synerg(ós) (see synergism) + Neo-Latin -ista -ist
British Dictionary definitions for synergist

synergist

/ˈsɪnədʒɪst; sɪˈnɜː-/
noun
1.
a drug, muscle, etc, that increases the action of another
2.
(Christian theol) an upholder of synergism
adjective
3.
of or relating to synergism
Word Origin and History for synergist
n.

1650s in theology (see synergism); 1867 in medicine, from Greek synergos "working together" (see synergy) + -ist.

synergist in Medicine

synergist syn·er·gist (sĭn'ər-jĭst)
n.
A synergistic organ, drug, or agent.